I finished "The Shack" last night. I don't want to ruin the plot for any of my readers (all five of you) who haven't read it but suffice to say, it's a good book when read in the proper perspective. I read LOTS of comments on it last night from people who loved it and people who hated it. Most of the haters disliked it because of the incorrect theology throughout the book. What I found interesting is some of what they claim as "incorrect theology" is only their interpretation of theology.
Now, I do have to point out that there will be times when you read this book that you will go "hmm, not sure I'm with you there." That's actually a good thing. We as Christians all too often insulate ourselves from things that might cause us to look at our own faith. But, if you don't have to work at it, is it really faith? I know I'm constantly questioning why God is working on something particular in my life. I've never had an experience like what is described in this book but I am 100%certain that my God is big enough and sovereign enough to pull off the encounter described if He saw fit.
In short, this book is recommended with caveats. Remember it is fiction, remember it's an allegory and remember, it's ONE man's opinion. I would also caution that if you are a new believer, read it along with a strong, growing believer so if you have questions, you can ask them of someone who either knows the answer or is willing to search for the Truth with you.